In a wireless communication system, transmission of data can take place by using a number of transmission techniques, such as frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), global system for mobile (GSM) communication, orthogonal frequency division multiple access (OFDMA), universal mobile telecommunications system (UMTS), interleaved frequency division multiple access (IFDMA), and so forth. For future broadband systems, in particularly for the uplink, Single-Carrier based approaches with orthogonal Frequency Division Multiple Access (SC-FDMA) are of interest. These approaches, particularly Interleaved Frequency Division Multiple Access (IFDMA) and its frequency-domain related variant known as DFT-Spread-OFDM (DFT-SOFDM), are attractive because of their low peak-to-average power ratio (PAPR), frequency domain orthogonality between users, and low-complexity equalization.
With IFDMA/DFT-SOFDM, multiple communication units can simultaneously transmit signals on orthogonal sets of frequency components. The signals from the different communication units propagate through different wireless channels in a wireless communication system and are received at a node as a composite signal comprising multiple signals from the different communication units. Therefore, a need exists for an efficient method and apparatus for processing the composite signal at the node in a wireless communication system and for detecting and separating the signals that are sent from the different communication units.
In IFDMA modulation, an IFDMA symbol is formed by the block repetition of a symbol block that contains combined subscriber signals, adding a cyclic extension, either before or after the modulation, and pulse shaping of the symbol block. The block repetition increases the bandwidth occupied by a single subscriber signal. Hence, the IFDMA symbol can be considered as a cyclic extension single carrier modulation, with special block repetition to create a “comb” like spectrum, which is interleaved with a number of subscriber signals.